The conventional one touch type dome shaped tent is illustrated in FIGS. 1 to 3, and the structure shown in these drawings is the basis for applying the device of the present invention.
FIG. 1 is a perspective view showing the structure of the spread state of the conventional one touch type dome shaped tent. As shown in this drawing, frame members 2 are joined to a hub 1 of the central peak of the tent, and the frame members 2 extend in all directions from the hub 1, thus the hub 1 forms an easily foldable central joint.
Each of the frame members 2 consists of an upper segment A, a middle segment B and a lower segment C. The three segments are joined into an integrated member, while each of the joining portions is provided with a hinge. Among the three segments, the upper segment A and the middle segment B are joined at an upper joint 3 in the form of , while the middle segment B and the lower segment C are connected at a lower joint 4 in the form of V. Thus the upper and lower joints 3, 4 perform folding movements in mutually opposite directions, in such a manner that one whole frame member 2 should form a zig-zag shape, as shown in FIG. 3.
Further, as shown in FIG. 2, the upper joint 3 is provided with a locking cap 5 to secure the end portion 6 of the joint and to prevent inadvertent folding. If the locking cap 5 is pushed down, the locked state is released, so that the upper joint 3 can be folded in the form of . In contrast to this, the lower joint 4 is not provided with such a locking device, but is provided with only a pivotal structure. But an end portion 7 of the joint supports the lower segment C so that the lower segment C can be folded only outwardly. Thus, if the tent is spread, the frame members are bent like a bow as shown in FIG. 2, while if the tent is folded, the frame members are folded in the form of V.
However, it has been proved through experience that the conventional one touch type dome shaped tent having the above described structure has problems yet to be solved. That is, there is no locking device on the lower joint 4. If a slight pushing force is applied when the tent is spread, the lower joint 4 can be inwardly folded as shown by an imaginary line S of FIG. 2, thereby making the tent collapse. Examples of such external forces T are an abrupt, strong wind; intrusion caused by children playing; kicking by a nocturnal walker and the like.
In an attempt to overcome the above described problems, a locking device may be provided also to the lower joint 4. However, in that case, the problem is that both the upper and lower locking devices have to be operated one by one by hand. Such a matter hurts the originally intended feature of the one touch type dome shaped tent which aims at the convenience and speediness of the folding operation. If one manipulation of the upper joint 3 causes the lower joint 4 to be operated (i.e., locked or released), it will be satisfactory; but, so far, such a device has not been invented.
Another problem lies in the joining between the joint and the frame member. Conventionally, the hole of the joint portion has a circular cross section, and the frame member also has a circular cross section. Therefore, even if the frame member is press-fitted into the hole of the joint portion, a clearance appears between the frame member and the hole. The result is that the frame members can be twisted, thereby bringing problems to folding or spreading the tent.